FIG. 1 illustrates a block diagram of a prior art wireless transmitter/receiver. Referring to FIG. 1, duplexer 100, in cooperation with an antennae, sends signals to a receiver 110 and will suffer transmitter feed thru in the duplexer from signals from a transmitter 120. During reception, duplexer 100 sends a signal of interest (SOI) (which is included in the entire receive band of the receiver) through a low noise amplifier (LNA) 130 and a surface acoustic wave (SAW) filter 140 to receiver 110. Receiver 110 uses a mixer 112 to mix a timing signal from a local oscillator (LO) 150 with the signal-of-interest (including the entire signal band pass as passed thru SAW filter 140) and down converting it to an IF, before demodulating the signal with a receiver processor 114. The demodulated signal is sent to a baseband processor 160 for further processing. During transmission, baseband processor 160 sends a signal to be transmitted to the transmitter device 120. Transmitter device 120 processes the signal with a transmitter processor 122, before using a mixer 124 to mix the signal with a signal from the local oscillator 150. The mixer 124 up converts the transmit signal to the desired RF transmit frequency. A high power amplifier (HPA) amplifies the signal, before being sent by duplexer 100 to the antenna for transmission over the air.
One of the common problems associated with wireless communications is unwanted signals intermixed with the information signal. These unwanted signals are referred to as interference. This interference can alter a radio frequency (RF) reception so that a receiver does not receive the information signal as intended.
To remove interference, filtering is often performed. The filtering may be performed in the analog or digital domain. In one commonly used technique, digital samples are low pass filtered to eliminate the higher harmonics above a baseband signal. However, this technique does not eliminate the interference due to the tails of the harmonic images that extend into the baseband signal.